Process for manufacturing plated products

ABSTRACT

A process for manufacturing plated products of metals in which a piece of one metal has its surface to be plated coated with a substance which decomposes releasing volatile organic compounds which protect the surface from oxidation by the atmosphere, while a second metal is cast adjacent the surface whereby a plating with high bond characteristics is formed.

United States Patent H 1 3,695,337

Grand Oct. 3, 1972 [5 PROCESS FOR MANUFACTURING 2,094,538 9/ I937lngersoll [64/ I00 PLATED PRODUCTS 2,29l .026 7/ I942 Chace 164/102Inventor: Rene Grand, Unieux France HOlmqulSt I [73] Assignee: Compagniedes Atelliers et Forges de FQREIGN PATENTS OR APPLICATIONS la Loire (SI.Chamond, Firminy, St. 70 03 3 1965 C d u 164 55 Etienne .lmbuolmr),Paris ana a France Primary ExaminerR. Spencer Annear [22] Filed: Oct. 7,1970 Attorney-Wenderoth, Lind 8L Ponack [30] Foreign Application PnorityData A process for manufacturing plated products of metals in which apiece of one metal has its surface to be Oct. 10, 1969 France ..6934722plated coated with a substance which decomposes [52] US. Cl .164] 100,164/55 relea ing volatile organic compounds which protect [51] hit. Cl...B22d 19/08 th rf fr m oxidation by the atmosphere, while a [58] Fieldof Search ..l64/55, I00, 10], 102 second m tal i a t adjacent thesurface whereby a plating with high bond characteristics is formed. [56]References Cited UNITED STATES PATENTS 17 Claims, 5 Drawing Figures2,042,800 6/1936 Pike ..l64/l0l X II I l I v I Y 2 '1" 3 \E i 5 I n asMr PAIENTEDnma m2 Fl (3. l

PROCESS FOR MANUFACTURING PLATED PRODUCTS I BACKGROUND OF THE INVENTIONThis invention relates to a new process for manufacturing platedproducts of metals such as steels, alloys or pure metals and moreparticularly but not exclusively forming a composite product from;

steels such as structural steel and tool steel with stainless steels orsteels which are resistant to high or low temperatures;

steels such as structural steel and tool steel with pure metals;

steels such as structural steel and tool steel with alloys based onnickel, chromium, molybdenum and tungsten, for example alloys comprisingvarious proportions of these elements.

stainless steels with pure metals and alloys as defined above.

Such composite products can be made from any combination of steels,alloys and pure metals, including pure metals bonded with one another.

The use of products made of stainless steels, heat-resistant or lowtemperature-resistant steels, alloys or pure metals, plated onstructural steels or with one another, has developed considerably inrecent years in all branches of industry (petrochemicals, chemicals,electronics. household goods).

Different plating techniques are at present used, depending upon theproducts to be produced (type dimension, shapes).

The two industrial methods which are generally used are:

a. Manufacture of a composite metal from at least two separate metalstrips, previously mechanically prepared to remove oxides and foreignmatter.

The composite metal is produced by rolling in a protective atmosphere.The strips are passed into furnaces at temperatures selected to give tothe final composite product the desired properties. This process is thusvery limited in its possibilities.

h. Manufacture of composite metal by hot rolling. The constituentelements are prepared as a sandwich, with the interposition, on thepreviously mechanically prepared plating faces, of a deposit ofelectrolytic iron or nickel, for the purpose of facilitating thephenomena of chemical diffusion and preventing any oxidation during thecourse of heating. Use is made of various assemblies, with or withoutthe interposition of a protective gas.

The application of this process is very difficult and its successdepends upon the precautions taken throughout the whole productionprocess.

From the metallurgical aspect, this process involves permanent risk oflocal failure to bond. in addition carbon diffusions, especially in thecase of plating stainless steels. may preclude the use of this processin certain cases of special corrosion resistance.

A product particularly one designed to resist corrosion at lowtemperatures or at high temperatures is very often a steel having a highcontent of inoxidisable elements and in particular has a surface which,during the heating operations, becomes covered with a continuous film,adherent and impermeable to oxides, which arrests the diffusionphenomena and thus compromises the adhesion of the plating metal.

SUMMARY OF THE INVENTION The present invention has as an object theproduction of plated products, the plating obtained having high bondcharacteristics capable of resisting low or high temperatures.

A further object is the production of plated products of a wide varietyof dimensions not just those which can be rolled.

A further object is to provide a plating process which is easy to applyand economical of time and materials.

Accordingly the invention provides a process for the production ofplated metal products in which a first metal piece has its surfacecoated with a layer of a substance, and a second metal is cast adjacentthat surface, said substance being such that it decomposes very close tothe liquid front, releasing volatile organic compounds which protect thefirst metal from oxidation by the atmosphere, and which ensure a goodcontact of the liquid metal with the cleaned surface of the first metal.

According to one particular embodiment of the in vention, the layer ofsubstance is a polyfluorethene. This may be applied by spraying orbrushing on, of an aqueous or alcholised dispersion of apolyfluorethene. or by any other means.

In one form the process starts with a metallic core, the surface ofwhich has been previously prepared and coated with a polyfluorethene,this core is then arranged inside an ingot mould or other mould, and aplating metal is introduced into the remaining part of the mould.

In the absence of a layer of substance such as polyfluorethene themetallic base piece, during the course of the casting, would be raisedto a high temperature such that it would progressively oxidize in theair. The oxide formed on its surface would constitute a barrier to thediffusion phenomena and would compromise the adhesion of the platingmetal.

ln the practice of the present invention during the course of casting,the substance such as polyfluorethene becomes progressively pyrolised atthe front of the liquid metal and emits gaseous vapors which protect thesurface of the base piece from oxidation. In this manner the adhesion ofthe plating metal to the base piece is ensured under excellentconditions.

The polyfluorethenes (for example the polytetrafluorethylene or thepolychlorotrifluorethylene or their derivatives) give satisfaction underthese circumstances because they possess simultaneously the followingcharacteristics; high chemical stability; :1 product which isnon-plastifiable at high temperatures; a product which isnon-thermo-hardening and non-thermoplastic (a gel at high temperature,this gel having high viscosity); absence of a true melting point;decomposition by pyrolysis, giving rise to fluorinated or chlorofluorinated compositions.

An important consequence of these properties is that the productdecomposes at the useful instant (and not before), very close to theliquid front, releasing volatile organic compounds which protect thesolid piece from oxidation by the atmosphere and which ensure a goodcontact of the liquid metal onto the previously cleaned surface of thebase piece.

In a general way the derivatives of ethylene, in which the hydrogenatoms are partially or wholly replaced by atoms of fluorine and/orchlorine, (e.g. su-

perchlorinated polyvinyl chloride), possess to a considerable extent theproperties described above and may thus be suitable for protecting themetal surface effectively from oxidation.

If an ingot, and not a casing, is used as the base piece, the compositeingot thus produced can then be rolled in accordance with normaltechniques and taking account of the restraints which are necessary indealing with the particular materials involved in the composite product.

The casting of the plating metal is preferably effective at source.However, this casting may be made directly and, if necessary, by meansof a ladle with one or more nozzles.

The base piece can be plated on one or both sides as desired, or twobase pieces can each be plated on a single face simultaneously in thesame mould. Such two pieces may be in contact at their faces which arenot to be plated and which are separated by an anti-sticking product,such as chromium oxide for example, or be assembled by a peripheral weldpreventing any penetration of liquid metal and preventing sticking ofthe surfaces in contact, or both be coated with an anti-stick productand welded peripherally.

The casting of the plating metal may be carried out under the protectionof an inert gas, such as argon. For this purpose the jet of platingmetal at its exit from the casting ladle is surrounded by such an inertatmosphere and/or the mould is placed under such atmosphere.

The principal advantages of the process according to the invention atleast in its preferred embodiments are:

case of application;

substantial economies compared with methods previously used;

substantially perfect plating;

extension of the possibilities of the use and production of platedproducts, by virtue of the improved properties resulting from theelimination of any harmful contact and other pollution.

Polyfluorethene coatings, due to their particular properties, bothphysical and chemical, enable exceptional cleanliness of the contactsurfaces to be achieved at the moment of casting, thus facilitating thenormal commencement of the diffusion phenomena leading to the productionofa plating with high bond characteristics.

Ultrasonic inspection of products formed by the invention exhibited asubstantially perfect bond between the base piece metal and the platingmetal.

Transverse sections made with a blow-torch using powdered iron confirmedperfectly the ultrasonic examinations and the substantially completeabsence of non-cohesion, even partial or local.

in order to make the invention more easily understood, there will now bedescribed by way of nonrestrictive example, four methods of realizationof the invention, reference being made to the accompanying drawings, inwhich:

FIG. 1 is a perspective view showing one form of vertically sectionedingot mould in which a base piece is suspended before casting;

FIG. 2 is a view similar to alternative form of mould;

FIG. 3 is a view similar to that of FIG. I further form of mould;

FIG. 4 is a view similar to that of FIG. I, with two contiguous basepieces to be plated; and

that of FIG. I showing an showing a FIG. 5 illustrates, in verticalsection, of forming a plated cast piece.

In all these examples a solid base piece of carbon structural steel isinvolved, which receives a plating of stainless steel cast at thesource, or indeed these two items may be reversed. The arrangements ofFIGS. 1 and 2 are for the plating of stainless steel on the two faces 2and 3 of a bloom 4 of carbon steel. For this purpose, a start is madewith a bloom 4 of carbon steel of dimensions 1.700 X 0.850 X 0.160meters, these dimensions constituting only an example, which iscarefully cleaned and, if it is not to be used immediately, has itssurface protected from oxidation and any external pollution by a coatingof a currently used protective product. At the last moment beforeplating this protective product is removed by a special solvent and thebloom is coated, by spraying or brushing its faces 2 and 3 with a layerof polyfluorethene arising, for example, from an aqueous or alcoholiseddispersion. This coating is then subjected to some fritting by moderateheating for a short period. The bloom is then carefully introduced intothe ingot mould 5, either suspended so as to leave underneath it a spacesufficient for the arrival of the plating metal (FIG. 1) or placed onthe bottom of the ingot mould if the arrival or the plating metal fromthe source takes place at the sides (FIG. 2). The plating metal arrivesduring the course of casting through the base of the mould as indicatedby the arrows and occupies the space 1. The jet of stainless steel, atits exit from the casting ladle, is protected by an argon atmosphere.

The arrangement of FIG. 3 is for forming a stainless steel plating on asingle face of a bloom of carbon steel. A bloom 6 of carbon steel isprepared as before, but the polyfluorethen is applied to only one face7. The bloom is then introduced into an ingot mould 8 in such a way thatthe large side 9 of the bloom 6 and the base which are not to be platedare placed up against one wall and the base of the mould. Stainlesssteel is then introduced as indicated by the arrow to fill the cavity10.

According to a variant the items are transposed, that is to say a bloomof stainless steel is prepared, and placed up against one wall of theingot mould, after its working face has been coated withpolyfluorethene, and carbon steel is cast, at source, into the remainingspace.

The arrangement of FIG. 4 provides for effecting simultaneously twosimple platings. For this purpose, two blooms H and 12 of stainlesssteel are placed back-to-back, an anti-stick layer 13 being placedbetween them. They are if necessary held in this position by aperipheral weld 14. The face 15 of each bloom which is to be plated iscoated with the layer of polyfluorethene, and the whole is introducedinto an ingot mould l6, either suspended, or placed on the bottom.Carbon steel is then cast at source into the space 17. Clearly thecarbon steel and stainless steel can be interchanged as before.

The arrangement of H6. 5 is for producing a plated shaped casting. Firsta carbon steel casting 18 is produced to the desired size and shape withthe omission at the faces which are to be plated of a thicknesscorresponding to the desired plating layer. The surface to be plated I9is then coated as described above. Finally, the cast piece 18 is placedaround a mould core 20 and the stainless steel is cast at source tooccupy the space 21 left between the mould core and the piece.

another method The process of the invention is applicable to themanufacture of numerous composite products such as castings, wire,strip, plates and tubes, with single plating, or double plating, orplating limited to certain parts of the desired final product.

lclaim:

l. A process for the production of plated metal products comprisingcoating the clean surface to be plated of a first metal piece with alayer of a derivative of ethylene, in which the hydrogen atoms arereplaced by atoms of the group comprising fluorine and chlorine andcasting a second metal adjacent to said surface so that said layerdecomposes close to the liquid front of said second metal releasingvolatile organic compounds.

2. A process according to claim 1, in which said derivative issuperchlorinated polyvinyl chloride.

3. A process according to claim I in which said derivative is apolyfluorethene.

4. A process according to claim 1 in which the layer of said derivativeis applied in the form of a dispersion in liquid.

5. A process according to claim I in which the casting of said secondmetal is carried out by top casting.

6. A process according to claim I in which the casting of the secondmetal is carried out directly.

7. A process according to claim 1 in which the second metal exits from acasting ladle in a jet which is surrounded by an inert atmosphere.

8. A process according to claim I in which the first metal piece isplaced in a mould into which the second metal is cast and the mould isplaced in an inert atmosphere.

9. A process according to claim 8 in which the inert atmosphere isargon.

l0. A process according to claim 1, in which the plating is carried outon two faces of the first metal piece.

II. A process according to claim I in which the plating is carried outon a single face of the first metal piece.

12. A process according to claim 1 in which the plating is carried outon a single face of two first metal pieces simultaneously, the twopieces being in contact at their faces which are not to be plated andbeing separated by an anti-stick product.

13. A process according to claim 12, wherein said anti-stick product ischromium oxide.

14. A process according to claim 12, in which the pieces are weldedperipherally at their faces which are not to be plated, the peripheralweld ensuring slight separation which prevents direct contact betweenthese two faces, thus enabling the two pieces to be subsequentlyseparated after plating.

15. A process according to claim 1 in which the first metal piece isplaced in a mould having walls and a base defining an aperture and thesecond metal is introduced into the mould through the aperture to fillthe space between the mould walls and the first piece.

16. A process for plating a cast piece which comprises coating thesurface of said piece to be plated with an organic substance whichdecomposes by pyrolysis to release volatile non oxidizing compositions,and then casting the plating metal to occupy the space left between themould and the piece.

17. A process for plating a cast piece defining a cavit which co risescoa in the surfaceof said iece to b e plated wiili an organic s ubstanceWl'llCl'l deco mposes by pyrolysis to release volatile non oxidizingcompositions, placing a mould core in the cavity, and then casting theplating metal to occupy the space left between said piece and said mouldcore.

2. A process according to claim 1, in which said derivative issuperchlorinated polyvinyl chloride.
 3. A process according to claim 1in which said derivative is a polyfluorethene.
 4. A process according toclaim 1 in which the layer of said derivative is applied in the form ofa dispersion in liquid.
 5. A process according to claim 1 in which thecasting of said second metal is carried out by top casting.
 6. A processaccording to claim 1 in which the casting of the second metal is carriedout directly.
 7. A process according to claim 1 in which the secondmetal exits from a casting ladle in a jet which is surrounded by aninert atmosphere.
 8. A process according to claim 1 in which the firstmetal piece is placed in a mould into which the second metal is cast andthe mould is placed in an inert atmosphere.
 9. A process according toclaim 8 in which the inert atmosphere is argon.
 10. A process accordingto claim 1, in which the plating is carried out on two faces of thefirst metal piece.
 11. A process according to claim 1 in which theplating is carried out on a single face of the first metal piece.
 12. Aprocess according to claim 1 in which the plating is carried out on asingle face of two first metal pieces simultaneously, the two piecesbeing in contact at their faces which are not to be plated and beingseparated by an anti-stick product.
 13. A process according to claim 12,wherein said anti-stick product is chromium oxide.
 14. A processaccording to claim 12, in which the pieces are welded peripherally attheir faces which are not to be plated, the peripheral weld ensuringslight separation which prevents direct contact between these two faces,thus enabling the two pieces to be subsequently separated after plating.15. A process according to claim 1 in which the first metal piece isplaced in a mould having walls and a base defining an aperture and thesecond metal is introduced into the mould through the aperture to fillthe space between the mould walls and the first piece.
 16. A process forplating a cast piece which comprises coating the surface of said pieceto be plated with an organic substance which decomposes by pyrolysis torelease volatile non oxidizing compositions, and then casting theplating metal to occupy the space left between the mould and the piece.17. A process for plating a cast piece defining a cavity which comprisescoating the surface of said piece to be plated with an organic substancewhich decomposes by pyrolysis to release volatile non oxidizingcompositions, placing a mould core in the cavity, and then casting theplating metal to occupy the space left between said piece and said mouldcore.